The frequency-temperature characteristic of a GT cut quartz oscillator is a function of the coupling between a shorter side vibration and a longer side vibration. The coupling state is changed by polishing a shorter side or a longer side of the oscillator. The best temperature characteristic is attained at a certain side ratio (the ratio between the shorter side and the longer side). In particular, a GT cut quartz oscillator employs the shorter side vibration as the principal vibration. A feature of the oscillator is that the frequency does not change materially even when the longer side direction is adjusted and that the adjustment of frequency and the adjustment of the temperature coefficient can be independently performed.
In accordance with the prior method of adjusting the frequency-temperature characteristic of a GT cut quartz oscillator, an oscillator blank which is slightly lower in frequency and more "negative" in temperature coefficient than the desired oscillator is first prepared. While checking the temperature characteristic of the oscillator, the longer side is polished so as to adjust the temperature coefficient to zero. Both sides of the oscillator are then polished so as to reduce the size of the oscillator while keeping the same shape in order to attain the desired frequency. The fine adjustment is laborious since it is very difficult to make the adjustment so as to satisfy both the temperature coefficient and the frequency.